Es·tu·a·ry n.; pl. Estuaries   [Written also æstuary.]
 1. A place where water boils up; a spring that wells forth. [Obs.]
 2. A passage, as the mouth of a river or lake, where the tide meets the current; an arm of the sea; a frith.
    it to the sea was often by long and wide estuaries.   --Dana.